Here are some pictures if you want to test your eyes or see the difference.
These work best on a ps3 or pc connected to a 1080p display with dot by dot, full, or pixel to pixel mode.
(The 360 unfortunately doesn't display 1080p images at full 1080p, some down and upscaling happens before the picture is shown)
It is probably easiest on a pc monitor as long as you display the pictures at the actual res.
Each picture is repeated, one at full res, one properly downscaled to a quarter res (2x2 pixels) and one at a third (3x3 pixels).
Now walk away as far as you need to, so you are sure you can't see any difference between the first and the second version of the picture.
Calculate the pixels per degree for that distance, half that value is the maximum your eyes can see. (for the display you are using)
